The concept of harnessing energy from moving water and the wind continues to be the source of research and innovation. The most common method used to harness energy from moving water involves building a hydroelectric dam and extracting energy by passing water through turbines. Building dams creates problems, including flooding of land, creating barriers to migrating fish and upsetting the natural high and low water flow cycles. Windmills are commonly used for harnessing wind energy. Windmills typically have a number of blades, wings or other fluid foils that rotate about a central, typically horizontally-oriented, drive shaft. Another type of energy-harnessing apparatus is a conveyor-type apparatus in which a number of fluid foils are carried by an endless chain passing between spaced-apart sprockets. Conveyer-type apparatus have been developed for use in both air and water. Some of these apparatus use flexible fabric as the fluid foils; see, for example, U.S. Pat. No. 443,641. Other conveyor-type apparatus use relatively rigid fluid foils; see U.S. Pat. Nos. 1,502,296; 4,049,300; and 4,563,168.